This invention relates generally to mouth nose masks, and more particularly to one that does not hinder normal breathing and allows a nasal cannula to be used for a single function or for dual functions of sensing inhalation and delivering a fluid, such as oxygen, when a human breathes either through the nose or mouth.
Nasal cannulas are commonly employed in the administration of gaseous fluids, such as oxygen, into the nasal passages of a convalescent human or those having respiratory ailments. Illustrations of nasal cannula can be found in U.S. Pat. No. 3,802,431. Nasal cannulas have been in use for a relatively long time for inhalation therapy.
The use of a nasal cannula for sensing inhalation has been recently accomplished and made possible by the development of highly sensitive inhalation sensors such as described in U.S. Pat. No. 4,745,925. A nasal cannula can be used for monitoring breathing and detecting apnea (the absence of breathing) by being connected to a highly sensitive inhalation sensor. The dual functions of sensing inhalation and administering fluids, such as oxygen, can be accomplished with a single cannula to determine the on-set of inspiration to trigger delivery of a specific dose of a respiratory gas through the same nasal cannula that is sensing inhalation.
A nasal cannula has the disadvantage that when a human breathes through his mouth the nasal cannula can not sense inhalation. A blockage of the upper nasal passageways, causing mouth breathing, can prevent proper administering of fluids, such as oxygen, to a human.
The purpose of the mouth nose mask which is positioned adjacent to a human's face and worn over a nasal cannula, is to deliver fluid being administered by a nasal cannula to a human's nose, or to the oral cavity when a human breathes through his mouth. Likewise, when a nasal cannula is used for sensing inhalation, a blockage of the mask user's upper nasal passages will result in some of the oral inhalation being diverted to a nasal cannula to allow sensing inhalation.
The advantage of using a nasal cannula for sensing is that a nasal cannula is more efficient, in that the most difficult sensing of inhalation is when breathing occurs through the nose, since the negative pressure can be as little as 0.001 of an ounce per square inch. A nasal cannula is most efficient in connecting the human nasal passageways to a highly sensitive inhalation sensor to detect the low negative inhalation pressure at a human's nostrils.
If a nasal cannula is replaced by a more common mouth nose mask used for inhalation therapy, with a connection to a sensor, it would be necessary for such a mask to have an air-tight fit to a human's face since the slightest leak will cause loss of the very low nasal negative pressure of inhalation. Such a mask, with connection to a sensor, would also require a valve that would close when a human inhales, and it would not be possible to mix outside air with fluids, such as oxygen, being administered.
The present mouth nose mask need not be an air-tight fit, as it has no valve and has an opening to the outside air, it is only required to divert a small amount of the large inhalation pressure from the oral cavity to a nasal cannula for sensing and allows air to enter the mask for mixing with a gas being administered. The construction of the mouth nose mask, according to the invention, is so simple, that it can be made disposable for single human use.